A Detailed Guide to Calendula Planting Techniques and Management Methods
Calendula, also known as changshengju, jinzhanhua, changchunju, huangjinzhan and so on, is a herbaceous flowering plant of the genus Calendula in the family Asteraceae. It originated in Europe and was introduced into China from abroad after the 18th century. After the 1980s, with the introduction of double-flowered, large-flowered and dwarf calendula varieties, research on cultivation and the development and utilization of calendula advanced rapidly in China. The calendula plant is dwarf, with dense flowers, brilliant and eye-catching colors, and a long flowering period. It is mostly used as a bedding material for flower beds, flower borders and flower mirrors, and can also serve as an edging plant for lawns. It is one of the most common herbaceous flowers in gardens and cities in early spring. In addition, calendula also has extremely high medicinal and economic value. Below, let us take a look at calendula planting techniques together!
Calendula Growth Habits
Calendula originated in southern Europe and along the Mediterranean coast. It is cold-tolerant, afraid of heat, and fond of a sunny, well-lit environment.
1. Temperature: The suitable growth temperature for calendula is 7-20 degC. Seedlings can withstand a low temperature of -9 degC in winter, and 10 degC is suitable for the growth of mature plants. If the temperature is too low, plastic film protection is needed, otherwise the leaves are prone to frost damage. When the winter temperature is above 10 degC, calendula will grow leggy. When the summer temperature rises, the stems and leaves grow vigorously, the flowers become smaller, and the petals decrease markedly.
2. Humidity: For calendula seedlings, slightly moist conditions are better, which is beneficial to stem and leaf growth and improves cold resistance in winter. For mature calendula plants, slightly dry conditions are preferable, which can control stem and leaf growth and avoid leggy growth. For indoor or greenhouse cultivation, the air humidity should not be too high, otherwise it is prone to disease. Ventilation should be strengthened to regulate indoor humidity.
3. Light: Calendula likes ample sunlight. In particular, seedling raising in sunny beds or cultivation in greenhouses both require sufficient sunlight, which is very beneficial to stem and leaf growth, making seedlings grow short, sturdy and uniform. If there are too many rainy and snowy days and light is insufficient, the basal leaves tend to turn yellow, and the roots may even rot and die.
4. Soil: Fertile, loose and well-drained sandy loam or potting mix is suitable. A soil pH of 6-7 is best; the plant will have more branches and produce larger and more numerous flowers.
Calendula Propagation Methods
Calendula is mainly propagated by sowing, and can also be propagated by cuttings. Autumn sowing or early spring sowing in greenhouses (or sunny beds) is commonly carried out. In the south, sowing can be done in multiple periods within one year, but autumn sowing is the main method. Calendula has strong adaptability and can overwinter in the open field. When sowing in summer, attention should be paid to shading and preventing heat stress. In the north, spring sowing is mostly used, generally carried out in April-May, flowering in early summer, safely passing the summer in cool places, and flowering again between September and October. Autumn sowing can also be used; after sowing, the young seedlings are moved into cold beds from late September to early October to overwinter, and in the second spring they are moved outdoors for cultivation; or they can be grown in pots, moved into a low-temperature greenhouse when frost comes to force flowering, maintaining 8-10 degC, to supply flowers in winter.
Calendula Seedling Raising Techniques
1. Time: The seedling raising time can be determined according to the transplanting time. Generally, seedlings are raised about 50d before transplanting.
2. Seedling raising method: Use greenhouse or sunny bed seedling raising, mostly small arched sheds. The seedbed should be chosen in a wind-protected, sunny place, preferably running east-west. The width and length of the seedbed should be suitable for the size of the film and convenient management; generally the width should not exceed 1.3m. The height of the arched shed should preferably be about 60cm. For the film, it is best to choose a drip-free film with good warming and heat preservation performance.
3. Site selection and bed preparation: Choose fertile, loose and well-drained sandy loam or potting mix. Harrow to a depth of 20-25cm so that the surface soil is soft and fine and the field surface is level. For every 667 sq m of seedbed, apply 4000kg of fully decomposed high-quality farmyard manure, 12kg of urea, 5kg of potassium sulfate, 70kg of phosphate fertilizer, and 30kg of fine sand, mix thoroughly and spread on the surface, then turn it into the plot, then harrow fine and level.
4. Seed treatment: First select the seeds carefully, remove impurities and shriveled seeds, and ensure the seeds are plump. Then sun the seeds to kill pathogens, enhance seed vigor and increase the germination rate. Before sowing, soak the seeds in warm water at 35-40 degC for 3-4h, remove them, rinse once with clean water, drain the water and then sow. To prevent seedling-stage diseases, thiophanate-methyl or chlorothalonil can be used for seed dressing.
5. Sowing: Sowing should be carried out on a windless, sunny day. On the day of sowing, irrigate the seedbed thoroughly, and sow once the water has seeped down. Use the broadcast sowing method: first mix the treated seeds with fine sandy soil, then spread them over the seedbed in 2-3 passes; do not sow too densely. After sowing, cover with sieved soil 0.7-1cm deep.
6. Seedbed management: The suitable germination temperature is 20-22 degC. Generally, seedlings emerge completely 6-7d after sowing. After the seedlings emerge completely, note that the temperature inside the seedbed must not exceed 30 degC, so as to avoid burning the seedlings and root rot. When the seedlings grow to about 3cm and the first pair of true leaves unfolds, attention should be paid to ventilation to prevent leggy growth. Keep the temperature inside the seedbed at 25-27 degC. Ventilation should be done at 8-9 a.m., and not during the high temperature at noon, so as to avoid damaging the seedlings. If windy and cooling weather occurs, stop ventilation. When the average outdoor temperature is steadily above 12 degC, choose a clear and windless day, uncover the film, and remove weeds in the seedbed. If water is lacking, spray once thoroughly, cover the film well, and enlarge the ventilation openings. Do not water the seedbed too frequently; it is best to keep the bed soil alternately dry and moist. When the outdoor temperature is steadily at 15 degC, the film should be uncovered to harden the seedlings. About 7d before transplanting, stop watering and carry out seedling hardening before transplanting, in preparation for transplanting.